An optical add/drop multiplexer (OADM) is configured to multiplex and route, in a wavelength division multiplexing (WDM) optical network, optical signals on different channels. The optical add/drop multiplexer is located on an optical network node, and the optical network node exchanges data with the WDM optical network using the optical add/drop multiplexer.
In the prior art, it is currently proposed that a microring resonant cavity is used as the optical add/drop multiplexer. For details, refer to FIG. 1.
As shown in FIG. 1, 28a and 28b are two optical waveguides, 26 is a microring resonant cavity, and a transmission direction of an optical signal in the microring resonant cavity is a counterclockwise direction. The waveguide 28a is connected to an optical network, and an optical signal is transmitted from right to left in the waveguide 28a. In an area in which the waveguide 28a is coupled with the microring resonant cavity, an optical signal that has a same wavelength as a resonant wavelength of the microring resonant cavity is extracted, and enters the waveguide 28b by passing through the microring resonant cavity. A transmission direction of the optical signal in the waveguide 28b is from left to right, and an extraction of the optical signal is completed. However, an optical signal that has a different wavelength from the resonant wavelength of the microring resonant cavity is not affected, and is still transmitted from right to left in the waveguide 28a. The waveguide 28b is connected to an optical network node on which the optical add/drop multiplexer is located, which is equivalent to that the waveguide 28b is connected to a local optical network node. An optical signal that needs to be inserted is transmitted from left to right in the waveguide 28b, and an optical signal that has a same wavelength as the resonant wavelength of the microring resonant cavity enters the waveguide 28a by passing through the microring resonant cavity. A transmission direction of the optical signal in the waveguide 28a is from right to left, and an insertion of the optical signal is completed.
The extraction means that an optical network signal in the optical network is downloaded to the optical network node on which the optical add/drop multiplexer is located; and the insertion means that an optical network signal on the optical network node on which the optical add/drop multiplexer is located is uploaded to the optical network.
A disadvantage in the prior art is that the optical add/drop multiplexer supports normal operation only in a single direction. As shown in FIG. 1, when an optical signal in the waveguide 28a is transmitted from right to left, it can be only set that, in the waveguide 28b, an inserted optical signal enters from the left, and an extracted optical signal goes out from the right. However, this setting further causes a limitation that transmission of an optical signal from left to right is not supported in the waveguide 28a; otherwise, an optical signal in this direction is also extracted by the microring resonant cavity.
A scenario is considered: Referring to FIG. 2A, for example, there are three optical network nodes: a node 1, a node 2, and a server node 3. The node 1, the node 2, and the server node 3 implement optical communication using an optical waveguide 4. Therefore, optical network signals in two directions need to be transmitted in the optical waveguide 4. For example, the optical add/drop multiplexer shown in FIG. 1 is disposed on the node 2, and therefore an optical network signal that is sent by the server node 3 to the node 2 and has a specific wavelength may be extracted by the optical add/drop multiplexer on the node 2. However, if optical network signals sent by the node 1 to the server node 3 also include an optical network signal having the specific wavelength, the optical add/drop multiplexer on the node 2 also extracts the optical network signal that is sent by the node 1 to the server node 3 and has the specific wavelength. As a result, the server node 3 cannot receive the optical network signal, thereby affecting a normal service processing process.
It can be learned that the optical add/drop multiplexer in the prior art supports optical signal transmission only in a single direction, which is likely to affect normal optical communication.